Existing technology allows a radiation sensor probe to be delivered to subsurface locations of suspected contamination through a predrilled bore hole or by a direct push-penetrometer delivering a radiation sensor probe to a desired location.
Currently, spectral gamma sensor probes developed by the U.S. Army Engineer Waterways Experiment Station, Vicksburg, Miss. include a gamma sensor probe for spectroscopic radiation analysis of subsurface soil formations. This type of probe requires a thick steel housing around the probe's radiation sensor portion to provide strength to the gamma detector during a direct penetrometer push operation. This operation includes an initial push of the gamma sensor probe to a particular subsurface depth, stopping the sensor probe, and then collecting data over a period of time at desired subsurface locations. The data collected generally requires long acquisition periods due to the sensor probe's steel structural housing surrounding the gamma detector. Limitations of this surrounding steel housing include: i) attenuation of the radiation reaching the gamma detector and ii) increased generation of background gamma radiation by bremsstrahlung-scattering radiation resulting from gamma radiation striking atoms in the probe's steel housing which in turn causes the generation of unwanted background gamma radiation that prolongs the above mentioned data acquisition periods for determining radionuclide contaminants. The invention herein solves these problems by providing a detachable and fall-away steel sleeve adjacent to the detector that minimizes attenuation of radiation energy and radiation scattering due to a steel probe housing surrounding the probe's radiation detector.